Control system for electric elevators



FIPBZIZ AU 252 EX Dec. 5, 1933.

; REFERENCE E. w. SEEGER EXAMINER CONTROL SYSTBI FOR ELECTRIC ELEVATORS Filed larch 14, 1932 Patented Dec. 5, 1933 UNITED STATES PATENT OFFICE CONTROL SYSTEM FOR ELECTRIC ELEVATORS Edwin W. Seeger, Wanwatosa, Wia, assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware This invention relates to control systems for electric elevators and particularly to means for stopping the car and/or maintaining the car level with any of its several landings.

An object of the invention is to effect automatic stoppage of the car when it reaches a desired landing.

Another object is to provide improved automatic leveling means effective when the elevator car is within a given distance from the landing at which it is to be stopped.

Another object is to provide means of the aforementioned character which are highly sensitive and accurate and which will cause the car to approach the desired level and maintain it at that level much closer than has been possible with systems known heretofore.

Another object is to provide means for the aforementioned purpose which employ a light beam and a photo-electric cell affected thereby to determine and control the exact position of the car.

Another object is to provide improved and simple means for causing the controller to respond to the indications of the light beam.

Another object is to provide a control system of the aforementioned character which requires no mechanical linkage between the car and the controlling means.

Another object is to provide asystem of the aforementioned character in which all current carrying parts are stationary and wherein the transmission of light from the source to the photo-electric cell is intercepted by an ,element which moves synchronous with the car.

Other objects and advantages will hereinafter appear.

Referring to the accompanying drawing, L 1? and I? are the terminals of a polyphase cur- .rent supply system, 1 is a squirrel cage induction motor having the terminals 1', 1 and 1 the terminal 1' being directly connected to the line L whfle the terminals 1 and 1 may be reversibly connected to the lines L and L through the electromagnetic switches 2 and 3 respectively.

An electromagnetic brake B has its winding con-' nected in parallel with motor terminals 1 and 1. The switch 2 has normally open contacts 2' and 2 normally closed contacts 2 and the mag- .net winding 2 while switch 3 has normally open contacts 3' and 3 normally closed contacts 8 and a magnet winding 3'. The controller also includes two electromagnetic relays 4 and 5 having respectively magnet windings 4- and 5' and normally open contacts 4" and 5''. Connected in series with the magnet windings 4 and 5- respectively are gaseous electron discharge tubes 6 and '7. The tube 6 has a cathode 6-, anode 6 and a control grid 6, while the tube 7 has a 00 cathode '7, anode 7 and control grid 7 The cathodes 6' and 7' may be heated in any well known manner. A control switch 8 having a contast lever 8* and stationary contacts 8'' and 8 is provided for selectively energizing the switches 2 and 3 for reversing the motor connections. The switch 8 has also a stationary contact 8 which is in engagement with the lever 8 when the latter is in the oil positions.

The motor drives an elevator cage 9. Fastened to the cage so as to duplicate its movement is a light shield in the form of a ribbon 10 of steel or other suitable material. Mounted stationary in the hatchway adjacent and on one side of the ribbon is a lamp or other light source 11. On the opposite side of the ribbon are two light sensitive cells 12 and 13. The ribbon is provided with perforations l4 and 15. The perforations 14 are located on one side of the ribbon so that light from 11 passes through at least one of the perforations 14 onto the cell 12 whenever the elevator is near but above one of the floors while the perforations 15 are so located that light from source 11 strikes the photo-electric cell 13 through one or more of the perforations 15 whenever the elevator is somewhat below one of the floor levels. The photo-electric cell 12 is connected between the grid 6 and cathode 6 of the tube 6, while the photo-electric cell 13 is connected between the grid 7 and the cathode 7- of the tube 7. A discharge impedance 16 is connected between the grid 6 and the line L while a similar discharge impedance 1'! is connected between the grid 1 and the line L An autotransformer 18 has its primary winding 18* connected across lines L and L, while its secondary winding is connected between line 1.? and the impedances 16 and 17. The two windings are so' connected that the grids 6 and 7 are negative with respect to their cathodes. When no light shines on the photo-electric cells a high negative. potential is impressed upon. the respective grid during that half cycle of the alternating current when the cathodes are negative with respect to the anodes. When the cells 12 and 13 are made conducting by light shining upon them, they re- 10%, duce the resistance between the grid and cathode of the respectivetube to which they are connected, thereby reducing the negative potential. of the grid and permitting the tube to conduct; current. 1 1 .110

The equipment operates in the following manner:

If the car stands still and the operator wishes to move it in a downward direction, he throws the lever 8 to the left thereby completing a circuit from line L to contact 8*, coil 2 contact 3 to line L. The switch 2 is thus energized thereby completing the circuit to the motor and brake coil B and causing the motor to operate the car in adownward direction. As the car approaches the level at which the operator wishes to stop, he moves the lever 8' to the central position thereby interrupting a circuit through the magnet winding 2 and de-energizing the switch 2 whereupon the motor is disconnected from the line and the car stops. However, it at this moment the car is in such a position that light from the source 11 passes through one of the perforations 14 onto the photo-electric cell 12, the grid 6 is rendered incapable of preventing the tube 6 from conducting during the positive half cycle of the alternating current, that is, when the cathode 6 is negative with respect to the anode 6 and thus the relay coil 4* is energized the circuit extending from line L over lever 8, contact 8 winding 4', tube 6 to line I This causes closure of contacts 4* and the establishment of circuit connections for the magnet switch 2, shunting the break effected by disengagement oi lever 8' from contact 8*. The motor thus remains energized and the elevator moves down until the light from the source 11 onto the light sensitive cell 12 is intercepted whereupon the grid 6 becomes highly negative with respect to its cathode and current flow through the tube 6 is interrupted. The magnet switch 2 is thereby tie-energized thus stopping the motor.

If the elevator should slide past the landing, light will 'pass through the perforations 15 onto the photo-electric cell 13 thereby causing the tube 7 to conduct current in the manner aioredescribed in connection with tube 6. Tube '7 thus energizes the relay 5 which in turn closes the energizing circuit of the magnet switch 3, said switch thereupon responding to connect the motor in the reversedirection to the line, thereby causing the elevator to reverse until it reaches the exact position relative to the landing, whereupon it is again disconnected ashas been described.

Ii the operator desires to move the car in the upward direction he moves the lever 8' to the right so as to make contact with the contact button 8 thereby energizing the coil 3 of the switch 8 and causing the elevator to operate in the reverse direction to that first described. Under these conditions the leveling means again operate in the manner already described.

While I have described my invention in connection with a single speed alternating current elevator installation, it'is obvious that it may also be employed in connection with other systerns of control and other sources of power pp y Likewise the system may obviously be modified to effect stoppage oi the car at a desired landing without the return movement upon overtravel.

It is also possible to arrange my control in a similar manner to obtain graduated speeds of the motor,. dependent upon the distance 0! the car from the landing.

While the ribbon 10 is shown attached to the bottom of the elevator car for purposes of illustration, it may also be attached to the top, in

which case it would be guided over rollers in the penthouse, adjacent to the motor, and the light source and photo-electric cells would also be installed in the penthouse, so as to concentrate all controlling apparatus in one place.

The contacts 8 and 8 may i! desired be arranged so that the lever 8' makes contact with contact 8 before it breaks circuit with either one' of the aforementioned contacts, thus insuring that upon movement of the control switch to stop position the leveling means become active prior to the disconnection of the motor from the line due to interruption of the running control circuit.

What I claim as new and desire to secure by Letters Patent is:

1. In combination with an elevator car and a motor therefor, or an alternating current source, a stationary source of light, an electromagnetic switch for energizing the motor to operate in one direction, a second electromagnetic switch for reversing the direction of the motor, a gaseous electron tube in circuit with each of said switches and said alternating current source and having a grid, a stationary photo-electric cell connected to each of said grids and a light screen in form oi a ribbon attached to the car and arranged to permit passage of light from said source to said photo-electric cells selectively-according to the position of said car and to intercept said light when the car is level with a landing.

2. The combination with an elevator car, a motor for driving said car, electromagnetic reversing means, and switch means for controlling the operation of said car between landings, oi stationary photo-electric means, a stationary source of light for illuminating said photo-electric means, a light screen in form of a ribbon attached to the car and arranged to permit passage or light irom said source to said photo-electric means in a given position of said car and to intercept said light when the car is level with a landing, and electronic means responsive to said photo-electric means and connected in circuit to control said reversing means to effect leveling of said car upon return of said switch means to the "02! position.

3. The combination with an elevator car, a motor for driving said car, electromagnetic reversing means, and switch means ior controlling the operation of said car between landings, stationary photo-electric means, a stationary source or light for illuminating said photo-electric means, a light screen in form of a ribbon attached tothecarandarrangedtopermitpassageot light from said source to said photo-electric means when the car is near a landing and to intercept said light when the car is level with such landing, and electronic means responsive to said photo-electric means and connected in circuit to control said reversing means to eflect leveling of said car upon return of said switch means to the "oi!" position.

4. The combination with .an elevator car, a motor for driving said car, electromagnetic reversing means, and switch means for controlling the operation of said car between landings, stationary photo-electric means, a stationary source illuminating said photo-electric means, a light screen in form of a ribbon attached to the car and arranged to permit passage of light from said source to said photo-electric means when the car is near a landing, and to'intercept said light when the car is level with such landing, and a gaseous electron discharge tube responsive to said photo-electric means and connected in circuit to control said reversin means to eflect leveling of said car upon return .0! said switch means to the 011" position.

EDWIN W. SEEGER. 

